This was in contrast to Dalton’s theory, which proposed that atoms were indivisible and did not have internal structure. Thomson’s theory proposed that atoms were made up of a positively charged sphere, similar to a pudding, with negatively charged electrons embedded within it, like plums in a pudding. This theory built on the earlier work of Dalton and others and provided a more detailed understanding of the structure of the atom. Thomson in 1897, following his discovery of the electron. Thomson’s Atomic Theory, also known as the Plum Pudding Model, was developed by J.J. Thomson discovered the electron, which led to the development of Thomson’s atomic theory, which suggested that atoms were composed of positively charged matter with negatively charged electrons scattered throughout. Related Post: Understanding Atoms and Molecules Thomson’s Atomic Theory Additionally, it was discovered that not all atoms of a given element are identical in mass, as isotopes of elements were discovered. For example, it was discovered that atoms were not actually indivisible and that they could be broken down into smaller particles. This principle helped to explain the behavior of chemical reactions and provided a foundation for the study of stoichiometry.Īlthough Dalton’s Atomic Theory was groundbreaking and provided a framework for understanding the behavior of atoms, it was later revised as new discoveries were made. The third principle was that atoms combine in simple, whole-number ratios to form compounds.ĭalton’s theory also proposed the concept of conservation of mass, which states that the total mass of the reactants in a chemical reaction is equal to the total mass of the products.

The second principle was that all atoms of a given element are identical in size, mass, and other properties, while atoms of different elements have different properties.The first principle was that all matter is made up of atoms, which are indivisible and indestructible.Dalton’s Atomic Theory was based on several key principles. However, it was not until the 1800s that scientists began to conduct experiments that supported the existence of atoms and provided a more detailed understanding of their properties. The history of atomic theory dates back to the ancient Greeks, who first proposed the idea that matter is made up of indivisible particles called atoms. This theory laid the foundation for modern atomic theory and provided a framework for understanding the properties and behavior of atoms. Conclusion The History of Atomic Theory Dalton’s Atomic Theoryĭalton’s Atomic Theory, developed by John Dalton in the early 19th century, is a set of principles that explained the nature of matter and the behavior of atoms.Dalton’s Atomic Theory was based on several key principles.

Bohr's atomic theory